What it looks like

This is how it looks:

300×50 (usually called a Mobile Banner)

A real example:

300×50 Advice for Site Owners

A 300×50 isn’t a bad way to monetise mobile inventory on your site. However It is unlikely to be your largest revenue driver. This is because it is not a very large ad, and cannot contain very interesting messaging.

If you receive a good amount of visitors from smartphones it is worth experimenting with adding this ad size to your site. Give it a few months and see if it makes you any money – and compare that to any loss of visitors you may experience.

Note: To avoid annoying your users, it is generally advised to run these ads with a way to close them.

300×50 Advice for Ad Buyers

300x50s are one of the smallest ad sizes. They can be effective if used right, and often don’t cost that much to run. They are especially useful as they can hit users at a different point than usual desktop ads.

To get the most out of a 300×50, make sure you have a concise message to convey and simple clear graphics. This way you can get your message across in a tiny space.